/*-------------------------------------------------------------------------
 *
 * params.h
 *      Support for finding the values associated with Param nodes.
 *
 *
 * Portions Copyright (c) 2012-2014, TransLattice, Inc.
 * Portions Copyright (c) 1996-2017, PostgreSQL Global Development Group
 * Portions Copyright (c) 1994, Regents of the University of California
 *
 * src/include/nodes/params.h
 *
 *-------------------------------------------------------------------------
 */
#ifndef PARAMS_H
#define PARAMS_H

/* Forward declarations, to avoid including other headers */
struct Bitmapset;
struct ParseState;


/* ----------------
 *      ParamListInfo
 *
 *      ParamListInfo arrays are used to pass parameters into the executor
 *      for parameterized plans.  Each entry in the array defines the value
 *      to be substituted for a PARAM_EXTERN parameter.  The "paramid"
 *      of a PARAM_EXTERN Param can range from 1 to numParams.
 *
 *      Although parameter numbers are normally consecutive, we allow
 *      ptype == InvalidOid to signal an unused array entry.
 *
 *      pflags is a flags field.  Currently the only used bit is:
 *      PARAM_FLAG_CONST signals the planner that it may treat this parameter
 *      as a constant (i.e., generate a plan that works only for this value
 *      of the parameter).
 *
 *      There are two hook functions that can be associated with a ParamListInfo
 *      array to support dynamic parameter handling.  First, if paramFetch
 *      isn't null and the executor requires a value for an invalid parameter
 *      (one with ptype == InvalidOid), the paramFetch hook is called to give
 *      it a chance to fill in the parameter value.  Second, a parserSetup
 *      hook can be supplied to re-instantiate the original parsing hooks if
 *      a query needs to be re-parsed/planned (as a substitute for supposing
 *      that the current ptype values represent a fixed set of parameter types).

 *      Although the data structure is really an array, not a list, we keep
 *      the old typedef name to avoid unnecessary code changes.
 * ----------------
 */

#define PARAM_FLAG_CONST    0x0001    /* parameter is constant */

typedef struct ParamExternData
{
    Datum        value;            /* parameter value */
    bool        isnull;            /* is it NULL? */
    uint16        pflags;            /* flag bits, see above */
    Oid            ptype;            /* parameter's datatype, or 0 */
} ParamExternData;

typedef struct ParamListInfoData *ParamListInfo;

typedef void (*ParamFetchHook) (ParamListInfo params, int paramid);

typedef void (*ParserSetupHook) (struct ParseState *pstate, void *arg);

typedef struct ParamListInfoData
{
    ParamFetchHook paramFetch;    /* parameter fetch hook */
    void       *paramFetchArg;
    ParserSetupHook parserSetup;    /* parser setup hook */
    void       *parserSetupArg;
    int            numParams;        /* number of ParamExternDatas following */
    struct Bitmapset *paramMask;    /* if non-NULL, can ignore omitted params */
    ParamExternData params[FLEXIBLE_ARRAY_MEMBER];
}            ParamListInfoData;


/* ----------------
 *      ParamExecData
 *
 *      ParamExecData entries are used for executor internal parameters
 *      (that is, values being passed into or out of a sub-query).  The
 *      paramid of a PARAM_EXEC Param is a (zero-based) index into an
 *      array of ParamExecData records, which is referenced through
 *      es_param_exec_vals or ecxt_param_exec_vals.
 *
 *      If execPlan is not NULL, it points to a SubPlanState node that needs
 *      to be executed to produce the value.  (This is done so that we can have
 *      lazy evaluation of InitPlans: they aren't executed until/unless a
 *      result value is needed.)    Otherwise the value is assumed to be valid
 *      when needed.
 * ----------------
 */

typedef struct ParamExecData
{
    void       *execPlan;        /* should be "SubPlanState *" */
    Datum        value;
    bool        isnull;
#ifdef XCP
    Oid            ptype;
    bool        done;
#endif
} ParamExecData;


/* Functions found in src/backend/nodes/params.c */
extern ParamListInfo copyParamList(ParamListInfo from);
extern Size EstimateParamListSpace(ParamListInfo paramLI);
extern void SerializeParamList(ParamListInfo paramLI, char **start_address);
extern ParamListInfo RestoreParamList(char **start_address);

#endif                            /* PARAMS_H */
